The present invention relates to a sealing construction for an electrical connection box which is connected to a wiring harness for a motor vehicle so as to perform branching of a circuit and a method of forming a packing used for the sealing construction.
An electrical connection box used for connecting a wiring harness for a motor vehicle to various electrical components through branching, for example, a junction box is arranged to reasonably and economically connect a wire through branching by concentrating branch connection points at one spot. In response to the recent rise of density of wires of the wiring harness, various types of electrical connection boxes have been developed.
In a known electrical connection box shown in FIG. 1, a circuit 2 and a casing 3 are accommodated in a rectangular main body 1 having a pair of locking portions 5b. A waterproof cover 4 having a pair of locking portions 5a engageable with the locking portions 5b is mounted on the main body 1 so as to be locked to the main body 1 through engagement of the locking portions 5a with the locking portions 5b of the main body 1. Meanwhile, as shown in FIG. 2, a packing 6 in a packing groove 4a of the waterproof cover 4 is brought into contact with a contact portion, i.e., an upper edge 1a of an outer peripheral wall of the main body 1 so as to waterproof the main body 1.
As shown in FIG. 3, the packing 6 is formed into an annular shape by cutting a continuous rubber string to a predetermined length and then, bonding opposite ends 6a of the cut rubber string to each other by adhesive. Meanwhile, several markings a for inspecting twist of the packing 6 are placed on a surface of the packing 6. Subsequently, the packing 6 is mounted on a jig (not shown) and then, the waterproof cover 4 is set to the jig such that the packing 6 is fitted into the packing groove 4a of the waterproof cover 4. Thereafter, the waterproof cover 4 is removed from the jig in a state where the packing 6 is fitted in the packing groove 4a. Then, by observing the markings a, it is inspected whether or not the packing 6 fitted in the packing groove 4a is twisted. If it is found that the marking a does not exist at a marking location, the packing 6 is twisted and thus, mounting of the packing 6 on the waterproof cover 4 is performed again.
However, in order to mount the packing 6 on the waterproof cover 4, many steps of cutting the rubber string to a predetermined length, bonding the opposite ends 6a of the cut rubber string to each other by adhesive, placing the markings a on the packing 6, mounting the packing 6 on the jig, setting the waterproof cover to the jig, removing the waterproof cover 4 from the jig and inspecting twist of the packing 6 are required to be performed.
This many operational steps lead to a time-consuming and troublesome operation, low working efficiency and high production cost. Meanwhile, since operation of mounting the packing 6 on the jig and then, inserting the packing 6 into the packing groove 4a should be performed manually, such a case may happen that sealing performance of the known electrical connection box becomes unstable due to insufficient insertion of the packing 6 into the packing groove 4a, etc.